Balance Sheet Offsetting (Repos - by maturity date and collateral type) (Details 1) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	$ 505,293	$ 523,378
Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	312,876	304,681
Debt Securities Issued by States and Political Subdivisions
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	3,790	22,640
Residential - Government Agencies
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	101,256	98,019
Residential - U.S. Government Sponsored Enterprises
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	87,371	98,038
Maturity Up To 90 Days [Member]
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	2,703	22,788
Maturity Up To 90 Days [Member] | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	0	0
Maturity Up To 90 Days [Member] | Debt Securities Issued by States and Political Subdivisions
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	1,200	22,050
Maturity Up To 90 Days [Member] | Residential - Government Agencies
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	1,503	738
Maturity Up To 90 Days [Member] | Residential - U.S. Government Sponsored Enterprises
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	0	0
Maturity 91 To 365 Days [Member]
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	2,590	590
Maturity 91 To 365 Days [Member] | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	0	0
Maturity 91 To 365 Days [Member] | Debt Securities Issued by States and Political Subdivisions
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	2,590	590
Maturity 91 To 365 Days [Member] | Residential - Government Agencies
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	0	0
Maturity 91 To 365 Days [Member] | Residential - U.S. Government Sponsored Enterprises
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	0	0
Maturity 1 To 3 Years [Member]
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	150,000	200,000
Maturity 1 To 3 Years [Member] | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	110,392	200,000
Maturity 1 To 3 Years [Member] | Debt Securities Issued by States and Political Subdivisions
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	0	0
Maturity 1 To 3 Years [Member] | Residential - Government Agencies
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	18,793	0
Maturity 1 To 3 Years [Member] | Residential - U.S. Government Sponsored Enterprises
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	20,815	0
Maturity After 3 Years [Member]
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	350,000	300,000
Maturity After 3 Years [Member] | Debt Securities Issued by the U.S. Treasury and Government Agencies
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	202,484	104,681
Maturity After 3 Years [Member] | Debt Securities Issued by States and Political Subdivisions
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	0	0
Maturity After 3 Years [Member] | Residential - Government Agencies
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	80,960	97,281
Maturity After 3 Years [Member] | Residential - U.S. Government Sponsored Enterprises
Securities sold under repurchase agreements
Securities Sold under Agreements to Repurchase	$ 66,556	$ 98,038